1. Field of the Invention
The present invention relates to a bulk diffuser, and a polarizing plate and a liquid crystal display apparatus comprising the same, which are capable of suppressing luminance of a liquid crystal display apparatus from being lowered by suppressing a variation of scattering characteristic under an influence of humidity and by dispersing or diffusing light, thereby decreasing color variation in different view angles.
2. Description of Related Art
A transmission liquid crystal display apparatus is a display component represented by a flat panel display, which is lightweight, thin, and low in electric power consumption; thus, it is broadly used for a liquid crystal television, a car navigation system, a desktop or notebook personal computer, a cellular phone, a monitor for amusement, industrial, medical purposes or the like. Especially, the demand for television is increased for the liquid crystal display apparatus. Therefore, the liquid crystal display apparatus is requested to have a wide view angle and less confusion of gradation characteristic and color variation in order to view an image having many halftones from different angles.
The liquid crystal display apparatus includes a liquid crystal panel and a backlight unit which faces the liquid crystal panel and provides light to the liquid crystal panel. The liquid crystal panel includes, for example, a liquid crystal cell including a liquid crystal composed of bar-shaped liquid crystal molecules and a pair of substrates having electrodes to apply a voltage to the liquid crystal interposed between these substrates, RGB color filters which are interposed between the liquid crystal cell substrates arranged at a front of the liquid crystal display apparatus on which an image of the liquid crystal display apparatus is displayed, and a pair of polarizing plates which transmit only unidirectional oscillating light respectively with the liquid crystal cell interposed therebetween.
A liquid crystal display apparatus is proposed in which a diffusing film is provided for enlarging a field of view at a display surface of the liquid crystal panel (i.e., the front of the liquid crystal display apparatus) or the like (e.g., refer to Japanese Unexamined Patent Application, First Publication No. H10-10513).
However, the liquid crystal display apparatus cannot suppress the color variation enough even though the liquid crystal display apparatus has effects of enlarging the field of view and suppressing an inversion.
Therefore, a large number of diffusing films which can suppress color variation in different view angles while enlarging a field of view and suppressing luminance reduction, contrast reduction, and blurs of an image or a liquid crystal display apparatus using the same are developed
A bulk diffuser is known as a diffusing film having a diffusion layer in which inner diffusion elements (particles) are dispersed in a forming material (medium).
However, the bulk diffuser having the inner diffusion elements dispersed in the forming material has a problem in which the dispersion characteristic greatly varies along with a variation of refraction index of the forming material. The bulk diffuser is disposed at a display surface of a liquid crystal panel or on a polarizing layer of a polarizing plate to be used for the liquid crystal display apparatus; therefore, the forming material is easily exposed to humidity in the atmosphere. The refraction index of the forming material tends to vary by moisture absorption. In addition, an acrylic resin, which is used for the forming material, has high moisture absorbency from the atmosphere and is easy to vary the refraction index; therefore, a variation of a diffusing characteristic is remarkable in the bulk diffuser formed of an acrylic resin.